Condensin is an essential protein complex required for mitotic chromosome condensation and genomic stability. In humans, condensin consists of a structural maintenance of chromosomes (SMC) heterodimer, hCAP-C and hCAP-E, which form the core complex, and three non-SMC accessory proteins hCAP-G, hCAP-H and CNAP1. CNAP1 contains a chromosome targeting domain, which appears to be critical for condensin recruitment to chromosomes. A recently discovered interaction between this domain of CNAP1 and a 120kDa nuclear protein may participate in the regulation of the chromosome targeting function of CNAP1. This 120kDa was identified to be poly(ADP-ribose) polymerase 1 (PARP1). PARP1 is known to participate in DNA repair, replication and transcription, raising the possibility that condensin may be involved in these cellular functions. The aims of this proposal are: 1) The biochemical dissection of the condensin/PARP1 interaction. Such an analysis will include mapping studies to determine protein domains in both CNAP1 and PARP1 critical for interaction, studies to determine the post-translational modification of condensin subunits by PARP1, and colocalization experiments conducted with the use of immunohistochemistry. 2) The identification of the in vivo significance of this interaction. The functional significance of this association will be examined using several methods including expression of dominant negative constructs, chromatin immunoprecipitation assays, and chemical inhibitors of PARP1. With the abrogation of this interaction, a unique condensin/PARP1 related phenotype may be observed, leading to a determination of functional significance. As the mechanisms of condensin regulation are poorly understood, this project will provide novel insight in the area of chromatin structural regulation. Such knowledge should advance research in the fields of cancer biology where genomic instability can result in oncogenesis. [unreadable] [unreadable]